The present invention relates to antenna systems. More particularly, the present invention relates to a disc antenna system.
U.S. patent application Ser. No. 09/064,525, entitled xe2x80x9cCommunications Systemxe2x80x9d and filed on Apr. 23, 1998, discloses a receiver system configured to receive a wave having a carrier frequency and an electric field vector, the terminus of which traces a nonlinear path within a plane transverse to an axis of wave propagation at an angular velocity corresponding to a rotation frequency between the carrier frequency and zero. FIG. 2 illustrates the path 99 traced by the extremity of such a rotating vector 96 that propagates along an axis 98. As shown in FIG. 1, such a wave, referred to herein as a xe2x80x9crotatingxe2x80x9d wave, can be received using three separate coplanar dipole (or monopole) antennas 10, 20, 30. The three dipole antennas may be, for example, separated by 120xc2x0.
Three taps 15, 25, 35xe2x80x94each located on a different one of the one of the dipole antennas 10, 20, 30xe2x80x94produce three signals, such as the signals 101, 102, 103 shown in FIG. 3. The three signals are then amplified by an amplifier system 40. Although a single block is used to represent the amplifier system 40 in FIG. 1, three individual amplifiers, such as three Low Noise Amplifiers (LNAs), may be used. Each LNAs is xe2x80x9cone-dimensionalxe2x80x9d in that each amplified signal does not reflect the amplitude and orientation of the received wave. The entire amplifier system 40 (such as the three LNAs taken together), however, is xe2x80x9ctwo-dimensionalxe2x80x9d because a complete picture of the amplitude and orientation of the received wave is maintained.
A nonlinear periodic path demodulator 50 receives the amplified signal (such as the three individual amplified signals), as well as information from a nonlinear period path frequency source 60. The amplified signal is demodulated with respect to the nonlinear period path and can then be demodulated by an information demodulator 70. The information signal or signals contained in the received wave can then be reproduced.
Although FIG. 1 illustrates a receiver system using three dipole antennas 10, 20, 30, a different number of dipoles can be used instead. For example, four dipoles separated by 90xc2x0 could be used to receive the wave. Moreover, the signal received by each dipole is added coherently while the noise received by each dipole is added incoherently. Thus, increasing the number of dipoles can improve the Signal-to-Noise Ratio (SNR) the receiver system.
Although increasing the number of dipoles improves the SNR, such an approach has disadvantages. For example, each dipole will generally require separate electronic components, such as separate LNAs, to process the signal associated with that dipole. That is, the use of 360 dipoles, each separated by 1xc2x0, would create a sensitive receiver system but would also require the use of 360 separate LNAs. Such a system would be both difficult and expensive to create.
Moreover, the separation between dipoles must be accurately maintained. With a three-dipole system, such as the one shown in FIG. 1, each dipole must be separated by substantially exactly 120xc2x0. With different numbers of dipoles and/or different spacing between the dipoles, the physical separation must likewise relate to the phase differences in the modulation envelopes of the received signals. As the number of dipoles increases, maintaining the accuracy of the separation between the dipoles becomes more difficult.
Although the above description relates to a receiver antennas and a receiver systems, those skilled in the art will appreciate that similar problems can arise with respect to transmitter antennas and transmitter systems.
In view of the foregoing, it can be appreciated that a substantial need exists for an accurate antenna system that solves the problems discussed above.
The disadvantages of the art are alleviated to a great extent by an antenna element having an interface portion and a two-dimensional amplifier system coupled to the interface portion of the antenna element.
According to one embodiment of the present invention, the antenna element is substantially an annular antenna element and an inner perimeter edge of the antenna element is coupled to the two-dimensional amplifier system. The two-dimensional amplifier system may comprise a plurality of one-dimensional amplifiers, each one-dimensional amplifier being coupled to the inner perimeter edge of the antenna element at substantially equally spaced angular positions. The two-dimensional amplifier system may also comprise a two-dimensional field effect transistor. The antenna element and two-dimensional amplifier system are configured to either receive or transmit a wave having a carrier frequency and an electric field vector, the terminus of which traces a nonlinear path within a plane transverse to an axis of wave propagation at an angular velocity corresponding to a rotation frequency between the carrier frequency and zero.
With these and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein.